Entity transfer
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Entity Transfer. Chapter 7. What We’ll Do . Types of Entity Transfers Model 7-1: Resource-Constrained Transfers Models 7-2, 7-3: Transporters Conveyors Model 7-4: Non-accumulating Model 7-5: Accumulating. Types of Entity Transfers So Far. Connect Zero-delay

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Entity Transfer

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Entity transfer

Entity Transfer

Chapter 7

Chapter 7 – Entity Transfer


What we ll do

What We’ll Do ...

  • Types of Entity Transfers

  • Model 7-1: Resource-Constrained Transfers

  • Models 7-2, 7-3: Transporters

  • Conveyors

    • Model 7-4: Non-accumulating

    • Model 7-5: Accumulating

Chapter 7 – Entity Transfer


Types of entity transfers so far

Types of Entity Transfers So Far

  • Connect

    • Zero-delay

    • Connection graphic vs. module Labels (no graphic)

  • Route

    • Non-zero-delay — constant, r.v., expression

    • Stations, animated Routes

    • Fixed routes vs. entity-dependent Sequences

  • Connect and Route both assume:

    • No limit on number in transit at a time

    • Entities have their own feet

Chapter 7 – Entity Transfer


New types of entity transfers

New Types of Entity Transfers

  • Resource-constrained transfers

    • Limit total number of entities in transit at a time

    • Entities still have their own feet

    • Telecommunications (number of packets),logistics (number of vehicles)

  • Material-handling devices

    • Transporters – fork lifts, trucks, carts, wheelchairs

      • Usually place limits on numbers, capabilities of transporters

      • Like a Resource, except moveable

    • Conveyors

      • Belts, hook lines, escalators

      • Usually limit space on conveyor, speed

      • Non-accumulating vs. accumulating

Chapter 7 – Entity Transfer


Model 7 1 small manufacturing system with resource constrained transfers

Model 7-1: Small Manufacturing System with Resource-Constrained Transfers

  • Original system (Model 6-2)

    • Assumed all transfer times = 2 minutes … keep (for now)

    • Parts have their own feet … keep (for now)

    • No limit on number of parts in transit at a time … dump

      • Now – no more than 2 parts can be in motion at a given time

      • If other parts are ready to go, they must wait until there’s room to go

  • Model via existing constructs — think creatively

    • Model “space” on the “road” as a Resource

    • Limit the number of Units of this Resource

    • Entity must Seize unit of “space” resource before beginning trip, Release it at end of trip

Chapter 7 – Entity Transfer


Two ways to model resource constrained transfers

Two Ways to Model Resource-Constrained Transfers

  • Both use a new Transfer Resource representing space on the transitways

    • Capacity set to 2 in Resource data module

  • Maybe the most obvious way (but won’t do) …

    • Before each Route module insert a Seize module to Seize one unit of Transfer (queue, priority details … see text)

    • After each Station module (except Order Release) insert a Release module to free up one unit of Transfer

Chapter 7 – Entity Transfer


Two ways to model resource constrained transfers cont d

Two Ways to Model Resource-Constrained Transfers (cont’d.)

  • Different way (will do, to illustrate new modules, set up for transporters and conveyors) …

    • Replace Route modules with Leave modules (Advanced Transfer panel)

      • Transfer Out: Seize unit of Transfer resource before leaving station

        • Resource, Resource Set, particular member of a Resource Set

        • Can specify priorities

      • Also contains the Route operation

      • Get individual queues, with animation, for parts waiting to go

    • Replace Station modules with Enter modules (Advanced Transfer panel)

      • Defines the Station

      • Option of an unload Delay time (0 for this model)

      • Transfer In: Release Transfer resource

  • Effect – slight increase in cycle times in system

Chapter 7 – Entity Transfer


Transporter concepts

Transporter Concepts

  • Carts, fork lifts, trucks, wheelchairs, people, …

  • When entity is ready to go somewhere, it needs to be “picked up” and moved

  • Use Transporters— “moveable” resources

  • Activities: Request, Transport, Free

    • Transporter Selection Rule: If > 1 transporter is available when Requesting

    • When freed and > 1 entity is waiting: Priorities, closest one

  • Two types of Transporters

    • Free-Path (we’ll do)

      • Travel time depends only on velocity, distance

      • Ignore “traffic jams” and their resulting delays

    • Guided (won’t do)

      • AGVs, intersections, etc.

Chapter 7 – Entity Transfer


The small manufacturing system with transporters

The Small Manufacturing System with Transporters

  • Have two carts to transport parts

    • A cart can carry one part at a time

    • Carts move at 50 feet/minute

      • Will need to specify accurate distances between Stations

    • It takes 0.25 minute to load part on a cart, 0.25 minute to unload it from a cart

  • Modify Model 7-1 to Model 7-2

Chapter 7 – Entity Transfer


The small manufacturing system with transporters cont d

The Small Manufacturing System with Transporters (cont’d.)

  • Create Transporter in Transporter data module (Advanced transfer panel)

    • Name = Cart, Capacity = 2, Velocity = 50

    • Default the Distance Set (later), Units = Per Minute, Initial Positions

      • Mind the units – consistency here, in Distance Set (later)

  • Animation picture for Cart Transporter

    • Transporter button , Animate Transfer toolbar

    • Identifier = Cart, pictures for Idle, Busy, Inactive states

    • Draw or copy from .plb picture libraries

    • Ride point (details in book)

    • Drop it anywhere in flowchart view (hidden during run)

Chapter 7 – Entity Transfer


The small manufacturing system with transporters cont d1

The Small Manufacturing System with Transporters (cont’d.)

  • Request a Cart – modify existing Leave modules

    • Delay = 0.25 Minute for load time

    • Transfer Out = Request Transporter

    • Transporter Name = Cart

    • Selection Rule = Smallest Distance

      • Applies when > 1 transporter is available

      • Others: Cyclic, Random, Preferred Order, Largest Distance (???)

    • Save Attribute = Cart # (remember which cart … for later)

    • Connect Type = Transport

      • Move Time disappears … determined by Velocity, Distances (later)

    • Station Type = Sequence

  • Instead of Leave: Request-Delay-Transport

    • More complex, more flexible – book has details, examples

Chapter 7 – Entity Transfer


The small manufacturing system with transporters cont d2

The Small Manufacturing System with Transporters (cont’d.)

  • Free the Cart – modify existing Enter modules

    • Delay = 0.25 Minute for unload time

    • Transfer In = Free Transporter

    • Transporter Name = Cart

    • Unit Number = Cart # attribute of part entity

  • Instead of Enter: Station-Delay-Free

    • More complex, more flexible – book has details, examples

Chapter 7 – Entity Transfer


Distances for transporters

Distances for Transporters

  • Define contents of Distance Set Cart.Distance

  • Distances (in feet) moved by parts:

    • Blank cells: part movements that don’t occur

  • Enter these data in Distance data module (Advanced Transfer panel)

    • Name = Cart.Distance

    • Stations button, add 11 rows with Beginning Station, Ending Station, Distance for above data

    • Direction is implied; could be asymmetric

Units!!

Units!!

Why are there 25 rows??

Chapter 7 – Entity Transfer


Animating transporter movement

Animating Transporter Movement

  • Add distances to animation

  • Delete all the old Route Path animation objects

    • But leave the Station animations

  • Add animated transporter distances with Distance button , Animate Transfer toolbar

    • Dialog, placement similar to Route Paths

    • Identifier = Cart.Distance

    • Click in Beginning Station marker, intermediate clicks, Ending Station marker

    • Options for Rotate, Flip

    • Grid, Snap to help place animated transporter distances

Chapter 7 – Entity Transfer


Parking areas for transporters

Parking Areas for Transporters

  • Animate transporters when they’re free

  • Parking button , Animate Transfer toolbar

    • Like a Queue animation – Point vs. Line, Shift, Rotate

    • Cursor becomes cross hairs, click near lower left of Station marker to start, click for first Point or head of Line

    • More clicks for more Points (double-click to end), or second click to end Line

    • Want enough points/space for all transporters (2 here)

    • Repeat for all Stations where Transporters could be freed

Chapter 7 – Entity Transfer


More distances empty transporters

More Distances — Empty Transporters

  • Above Distances incomplete — only for part movements along their sequences

  • Transporters must also move when empty (deadheading)

    • In general, n(n - 1) distances need definition for network with n nodes

    • Some not possible — Order Release to Exit System

  • 14 more distances to define in Distances data module (not grayed):

Chapter 7 – Entity Transfer


Model 7 3 refining the animation for transporters

Model 7-3: Refining the Animation for Transporters

  • As it stands, Part Entities disappear from animation when waiting to be picked up by a Cart Transporter

    • Model logic OK … get right answers … animation is flawed

  • Solution – Storage for entity to reside in, be animated, while it waits for something (here, a Cart Transporter)

    • Can get statistics on numbers in Storages

  • But Storages not available with modules from Advanced Transfer panel

    • Use lower-level SIMAN modules from Blocks panel … see book for specific details

Chapter 7 – Entity Transfer


Conveyors

Conveyors

  • Replace Transporters with a conveyor

  • Loop conveyor to follow main path, clockwise

  • Six entrance/exit points

    • Load, Unload takes 0.25 minute

    • Each part is 4 feet per side, but want 6 feet of conveyor space for clearance on corners

  • Speed = 20 feet/minute

  • Distances:

Units!!

Chapter 7 – Entity Transfer


Conveyor concepts

Conveyor Concepts

  • Entity to be conveyed must wait for space

  • Conveyor consists of cells

    • Equal size, constantly moving – think of a narrow escalator

  • Entities might require multiple contiguous cells

  • Must define cell size; tradeoff involved:

    • Small cells: accurate model but slow execution

    • Large cells: just the opposite!

  • Entities Access space, Convey, and Exit

  • Conveyor = series of linear Segments

    • Each segment starts and ends at a Station

    • Link to form loops, diverge points, converge points

Chapter 7 – Entity Transfer


Types of conveyors

Types of Conveyors

  • Both travel in a single, irreversible direction

  • Nonaccumulating: belt, bucket line, escalator

    • Spacing between entities on it doesn’t change

    • Entire conveyor stops for entity Access/Exit if Load/Unload time is > 0

  • Accumulating: rollers, freeway

    • Conveyor never stops moving

    • If entity on it stops to Exit, other entities behind it are blocked and bunch up (entities ahead of it keep moving)

    • When blockage ends, blocked entities go on but maybe not all at once (spacing requirements)

Chapter 7 – Entity Transfer


Model 7 4 small manufacturing system with nonaccumulating conveyors

Model 7-4: Small Manufacturing System with Nonaccumulating Conveyors

  • Modify Model 7-1 (resource-constrained transfer)

  • Define new Variables Load Time and Unload Time, each with initial value 0.25

  • Delete all the Route Paths

  • Define Conveyor via Conveyor data module, Advanced Transfer panel

    • Conveyer = Loop Conveyor

    • Segment Name = Loop Conveyor.Segment

    • Type = Non-Accumulating

    • Velocity = 20 (feet), Units = Per Minute

    • Cell Size = 3 (feet)

    • Max Cells Occupied = 2 (cells per entity)

Units!!

Units!!

Chapter 7 – Entity Transfer


Leave enter modules for conveyor

Leave, Enter Modules for Conveyor

  • Change each Leave module

    • Delay = Load Time, Units = Minutes

    • Transfer Out = Access Conveyor

    • Conveyor Name = Loop Conveyor

    • # of Cells = 2

    • Connect Type = Convey

  • Change each Enter module

    • Delay = Unload Time, Units = Minutes

    • Transfer In = Exit Conveyor

    • Conveyor Name = Loop Conveyor

Chapter 7 – Entity Transfer


Conveyor segments

Conveyor Segments

  • Define one-way lengths (in feet) of segments

  • Segment data module, Advanced Transfer panel

    • Name = Loop Conveyor.Segment

    • Beginning Station = Order Release

    • Next Stations button

      • Name Next Station in correct sequence

      • Give distance (in feet) to this next station

  • Segment animation

    • Put Station markers in front of each Resource picture

    • Segment button , Animate Transfer toolbar

    • Dialog, crosshairs, clicking just like Distances for Transporters

      • Except here, have to place only 6 Segment animations

Chapter 7 – Entity Transfer


Conveyor statistics

Conveyor Statistics

  • Run/Setup/Project Parameters to check Conveyor Statistics

  • Get percent of time blocked (stopped)

  • Utilization statistic is average percent of space occupied on conveyor (not percent of time that a part was on the conveyor)

  • To see conveyor stop (it’s nonaccumulating) more clearly, change Load Time and Unload Time to much greater values than 0.25

    • Could do this during run with VBA (Chapter 9), or Run Controller – see text for details – but makes output statistics nearly impossible to interpret

Chapter 7 – Entity Transfer


Model 7 5 change conveyors to accumulating

Model 7-5: Change Conveyors to Accumulating

  • Conveyor module

    • Change Conveyor Type to Accumulating

    • Accumulation Length = 4 (in feet), amount of space the accumulated parts need on the conveyor

  • Running, see very little accumulation in animation

    • To see more, increase Load Time and Unload Time

Chapter 7 – Entity Transfer


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